89 firebird gta Starting and stalling problems

My nephew has a 89 Firebird GTA that has a problem of stalling after about 20 minutes of running time.
The car will not restart unless it is completely cooled down.
I have replaced the fuel filter and igniyion coil for him but there is still no change.
Any ideas on what to try next ????

First things first 3rd Gen TA's had horridly designed gastanks you can stall the cars out on 1/3rd of a tank by racing it up a hill. If it does it with a full tank id try replacing the fuel pump and cleaning the gas tank. ive seen problems where people stick condoms in your tank and when you go uphill the pump catches the condom and stalls cause no gas and as the pumps suction wears it releases. The pump might also just be going bad or might have a bad connection.

Really doubt this one will help.
I'm not to sure but i know alot of newer cars have problems because the computers require a certain voltage so check the groundwires get a voltmeter out and check it good. The first thing they do with any car you take to a gm dealership is test it with a voltmeter and throw a new battery on it.

Need a little more information out of ya.

When it doesn't restart does the engine turn over?

Mileage?

Last time spark plugs/wires were changed?

The car has about 110 k miles on it. The plugs and wires were changed 2 years ago. And the car does turn over it just will not start once it is hot.

Did you ever figure out what the problem was? I have the exact same problem.

We are still trying to figure this one out ???

need to check and see what yer loseing when it dies fuel or spark so put a fuel pressure gauge on it and a in line spark tester and let her run and watch yer fuel pressure
if it stays good have a helper crank the car and see if it has spark if not you changed the coil so now you need a module if fule pressure fall below about 45 you need a pump (if you need a pump have fun) :eek7: man those suck

If it's only doing it when hot, I'd start looking at the EGR valve to see if the diaphram is bad or if you have a plug in the pintle. A faulty EGR valve will definitely cause problems when the car is warm.